Throughout the world liquids and gases, such as fuels, are distributed through pipeline networks. The pipelines generally constitute large 40 foot long, 6-60 inch diameter sections of pipe that are welded together and buried underground. The pipelines follow the general contour of the earth and must be routed around natural and man-made obstacles. Rather than forming curves in a pipeline by welding short sections of pipe at angles to each other, curves are formed by bending sections of pipe on site as the pipeline is being built. Bending the pipe minimizes the number of welds and enhances the reliability of the resulting pipeline. Because of the size of the pipes being bent, pipe bending equipment is generally massive in nature and hydraulically operated. Typically, hydraulic pressure for operating the pipe bending equipment is provided by a hydraulic pump driven by an internal combustion engine. Such pipe bending machines are disclosed in U.S. Pat. Nos. 3,834,210; 3,851,519; and 5,092,150, the disclosures of which are incorporated herein by reference.
As is customary with large diameter pipes, a bend in each pipe is accomplished by making numerous small bends, each spaced from the other along the length of the pipe. For example, several half-degree, incremental bends spaced along a length of pipe may be used to create an overall curve of several degrees. The operator of a pipe bending machine is in full control of the number of incremental bends to be made, the spacing between the incremental bends, as well as the extent of each incremental bend in the pipe. Skilled operators can efficiently control a pipe bending machine to consistently form accurate bends in the pipes, while minimizing pipes that are damaged, under bent, or over bent. While it is possible to make consistent bends, to a certain extent, variations occur due to the skill and judgment of an operator and to differences between operators.
As will be described below, consistently achieving accurate, consistent, damage-free, pipe bends is dependent on the proper positioning of the pipe, stiffback, and pin-up shoe of the pipe bending machine. Typically, positioning the stiffback and/or pin-up shoe is done by a combination of visual, tactile, and/or audible cues that an operator acquires through experience. For example, an experienced operator can determine when the pin-up shoe is properly positioned by listening for a change in the sound of the engine. However, a lack of experience, fatigue, distractions, and environmental considerations may lead to improper positioning of the stiffback and/or pin-up shoe, contributing to variations in pipe bends or even damage to a pipe. It would therefore be desirable to provide a system to aid the operator in positioning the pin-up shoe and stiffback.
Ensuring that the pipe and pin-up shoe are properly positioned is also time-consuming. First, the stiffback is raised to bring the pipe just to the point of contact with the bending die. This is called the ‘level’ or ‘zero’ position. The pin-up shoe is then brought up to support the free end of the pipe. The stiffback is then raised or pivoted to incrementally bend the pipe around the bending die. Finally, the stiffback and pin-up shoe are lowered. If further bends are required, the pipe is moved axially to a new bend position, the stiffback and pipe are brought to the level position, the pin-up shoe is raised to support the pipe, and then the stiffback is raised to bend the pipe. Bringing the stiffback and pipe to the level position prior to each bend so that the pin-up shoe can be accurately positioned reduces the throughput of the pipe bending machine. It would therefore be desirable to provide a system to speed up pipe bending by reducing the time needed to position the pipe, stiffback, and/or pin-up shoe. It would also be desirable to eliminate the need to bring a pipe to the level position prior to each bend.
It can be seen from the foregoing that a need exists for a system to aid the skilled operator in forming incremental bends with a high degree of repeatability and accuracy, and to improve the speed at which pipes may be bent. Because existing pipe bending machines lack such a system, a further need exists for a system that is easily retrofitted to existing pipe bending machines.